Abstract 15456: In-vitro Assessment of Phrenic Nerve Cryothermal Injury
Background: Phrenic nerve (PN) injury may result from transcatheter ablations for the treatment of arrhythmias. Cryoballoon ablation has been reported to cause phrenic nerve (PN) injury: occasionally resulting in diaphragmatic hemi-paralysis. To date, the tolerance of the phrenic nerve to cold energy on short timescales is largely unstudied.
Methods: Swine phrenic nerves (n=12) were harvested and the fatty sheath dissected from the nerve. The PNs were then placed in a nerve recording chamber (ADInstruments, Colorado Springs, CO) with a custom built thermocouple array. Stimulus of 1 V and 0.1 mS were applied to the proximal end of the nerve. Propagated compound action potentials (CAPs) were recorded pre- and one hour post-ablation. A 3-5 mm thick section of striated muscle was placed on top of the nerve/thermocouple array to reduce the cooling power of the catheter. A Freezor Max (Medtronic, Minneapolis, MN) catheter was placed in contact with the muscle and a one minute ablation applied while nerve temperatures being recorded.
Results: The figure below displays cooling profile and recovery relationship. The table summarizes characteristics of the CAPs pre- and post-ablation for nerves that recovered. The p-valued were calculated using a paired t-test.
Conclusion: The data suggests that cooling to subzero temperatures will often cause PN CAPs to cease, indicating injury/death. For nerves that elicited post-ablation CAPs, reduction in amplitude was the recorded parameter with the greatest change. These data support the notion that cooling a PN to low, suprazero temperatures, may cause clinically relevant changes in diaphragmatic function.
- © 2013 by American Heart Association, Inc.